1. Field of the Invention
The present invention relates to a liquid crystal display apparatus including color filters of RGBW mosaic arrangement and a method of driving the same.
2. Description of the Related Art
Conventionally, color display is provided using display pixels each including sub-pixels corresponding to a plurality of colors. For example, in a display apparatus including color filters with an RGB stripe arrangement, in which the three colors of red (R), green (G) and blue (B) are repeatedly arranged in the row direction, each of the display pixels corresponding to the three RGB colors forms a sub-pixel. Such a display apparatus provides color display by handling the sub-pixels of the three colors as the display pixel, and displaying the sub-pixels of the three colors in spatial division according to image data input by a unit of the display pixel.
Further, sub-pixel rendering has recently been used as a technique for enabling display of high-resolution images with a small number of display pixels. The sub-pixel rendering technique is a technique of applying a grayscale signal to be applied to a sub-pixel corresponding to a color in an arbitrary display pixel by superimposing the grayscale signal on sub-pixels arranged in the periphery of that pixel. By using such a sub-pixel rendering technique, it is possible to provide display with the resolution of the same level as that of the conventional RGB stripe arrangement, even if the number of sub-pixels is decreased to ⅔ of that of the conventional RGB stripe arrangement. By decreasing the total number of sub-pixels, it is possible to increase the pixel area of each sub-pixel to 3/2, and achieve a high aperture ratio.
Further, as an application of the sub-pixel rendering technique, there is proposed a liquid crystal display apparatus including color filters in which four sub-pixels of R, G, B and W [white] are arranged in a mosaic pattern(hereinafter referred to as RGBW mosaic arrangement), instead of the RGB stripe arrangement. By providing display using the sub-pixel rendering technique on such a liquid crystal display apparatus including color filters with the RGBW mosaic arrangement, it is possible to achieve improvement in white luminance (white transmittance) because of introduction of white pixels, as well as the high aperture ratio.
Liquid crystals used as display pixels of a liquid display apparatus have a characteristic that its properties are deteriorated by prolonged application of a direct-current voltage. The display pixels of liquid crystal display apparatuses are therefore generally driven by an alternating-current voltage, for the purpose of longer operating life and stabilized display of the liquid crystal display apparatuses. Dot inversion drive, which inverts the polarity of a voltage to be applied to display pixels by a unit of a sub-pixel, is known as an approach for the alternating-current voltage drive. It is also possible to suppress flicker at the time of display by using the dot inversion drive in alternating-current voltage drive of liquid crystals.
Alternating-current voltage drive is needed at the time of driving a liquid crystal display apparatus with such an RGBW mosaic arrangement. When dot inversion drive is simply applied to a liquid crystal display apparatus with the RGBW mosaic arrangement, flicker increases compared to a case where dot inversion drive is applied to a liquid crystal display apparatus with the RGB stripe arrangement. This is because sub-pixels of the same color in the same row have the same polarity when the conventional dot inversion drive is applied to a liquid crystal display apparatus with the RGBW mosaic arrangement as shown in FIG. 8B, while the polarities of the sub-pixels of the same color in the same row alternate (the polarity is reversed every other pixel of the same color) and flicker is reduced when the conventional dot inversion drive is applied to a liquid crystal display apparatus with the RGB stripe arrangement, as shown in FIG. 8A.
Thus, when dot inversion drive is simply applied to a liquid crystal display apparatus with an RGBW mosaic arrangement, flicker is increased, which reduces the effect of the dot inversion drive to reduce the flicker.